Formation of the Structure of Peat Coke in the Presence of Iron Oxides
Abstract Generated abstract
This study examines how finely dispersed iron oxides affect the porous and crystalline structure of peat coke formed during pyrolysis. Peat and peat, ore moldings containing iron oxide were coked under controlled laboratory conditions, then analyzed by mercury porosimetry and X-ray diffraction after de-ashing. The results indicate that iron oxide additions alter pore-size distribution by increasing porosity within the measured range and shifting pore maxima during coking, while higher temperatures promote pore development and burnout associated with oxide oxygen. X-ray data suggest that iron oxides also favor ordering and growth of coherent scattering regions in coke carbon, producing larger crystallites at 1000 and 1200°C than in coke made from peat without additives.
Full Text
- I. M. Gibalo. Analytical Chemistry of Niobium and Tantalum. Moscow, 1967.
- I. K. Stepanova, S. I. Sinyakova. Zav. lab., vol. 33, 931, 1967.
FORMATION OF THE STRUCTURE OF PEAT COKE IN THE PRESENCE OF IRON OXIDES
N. P. Antonov, S. I. Smolyaninov, V. P. Zaryuto, G. L. Markelova
The properties of solid residues from the pyrolysis of peat depend to a considerable extent on their structure.
In the present work, data are presented from a study of the porous structure of peat and peat-ore materials and of the regions of coherent scattering of X-rays by coke carbon.
Peat moldings prepared from high-moor peat (degree of decomposition 20–25%, moisture content 88.2%, ash content 4.9%) and peat-ore moldings with an addition of iron oxide amounting to 24.84% on a dry-substance basis were coked in a laboratory shaft furnace at a heating rate of \(5^\circ/\text{min}\), with a one-hour holding period at the end of the coking interval. The porous structure was studied by the Plachenov method /1/ on a mercury porosimetric apparatus. The range of pores studied had an effective radius from 60 to 360000 Å.
To investigate the regions of coherent scattering of X-rays, the samples were de-ashed according to the method /2/. X-ray patterns were recorded on a DRON-1 unit, with a copper anode, an anode voltage of 30 kV, and an anode current of 20 mA. The determination of the crystal size and the half-widths of the interference maxima was carried out according to /3/. Crystals of precipitated, calibrated sodium chloride were used as the standard for determining the instrumental half-width of the interference peaks.
The mercury-porosimetry data show that the peat and peat-ore materials are characterized by a polydisperse porous structure. The introduction of iron oxides into the peat promotes an increase in the number of pores in the studied interval compared with peat without additives. The introduction of fine particles of iron oxide into pores larger than 360000 Å partially fills them; “fragmentation” of large pores into smaller ones occurs, as a result of which the porosity in the pore-radius interval 360000–60 Å increases, and the number of porosity maxima also increases. Thus, if in the initial-
in the sample without iron oxide there are three maxima, corresponding to pores with radii: 1—more than 50000 Å, 2—50000–13000 Å ($\lg r = 4.7–4.1$), 3—13000–1600 Å ($\lg r = 4.1–3.2$), whereas in the peat-ore material there are six of them. During coking of the peat-ore materials, the porosity maxima shift into the region of larger pores. The pores develop. In samples without additions of iron oxides, the first maximum shifts into the region of larger pores, while the second shifts into the region of small pores and merges with the third.
The data of X-ray diffraction analysis (table) indicate that the initial peat has elements of a crystalline structure, whose interference maxima on the X-ray diffraction patterns have a blurred shape and low intensity. This indicates that the regions of coherent scattering do not have constant crystal-lattice parameters, that their number is small, and that their size is slightly greater than 20 Å.
Table
Structural parameters of solid residues from heat treatment of TPM and peat
| Sample | Treatment temperature, °C | $d$, Å | $\gamma$, mm | $\beta 10^{-3}$, rad | $\beta$, rad | $L$, Å |
|---|---|---|---|---|---|---|
| Peat | initial | 3.42–3.39 | 23 | 16.15 | 15.7 | 90 |
| Peat | 400 | – | – | – | – | <20 |
| Peat | 800 | – | – | – | – | <20 |
| Peat | 1000 | 3.491–3.469 | 39 | 27.80 | 27.5 | 51.5 |
| Peat | 1200 | 3.389–3.394 | 208 | 21.40 | 20.95 | 67.5 |
| TPM | initial | 3.42–3.39 | 23 | 16.15 | 15.7 | 90 |
| TPM | 800 | – | tr. | traces | – | 20 |
| TPM | 1000 | 3.399–3.387 | 170 | 21.3 | 20.93 | 68 |
| TPM | 1200 | 3.391–3.370 | 176 | 14.1 | 13.52 | 104.5 |
During coking up to 400–600°C, disappearance of the interference maxima is observed, which apparently is associated with rupture and fragmentation of the lattice packets into smaller ones. A further increase in temperature (above 800°C) promotes ordering and growth of the regions of coherent scattering, while the oxides
up to the temperatures investigated ($1200^\circ$C) promote the formation of a crystalline carbon structure. Thus, if at a temperature of $1000^\circ$C peat crystallites without iron oxide additions have an average size of 51.5 Å, then with additions they are 68 Å, and at $1200^\circ$C, respectively, 67.5 and 104.5 Å.
Conclusions
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The introduction of finely dispersed iron oxides into peat contributes to a change in the character of the pore-size distribution.
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Increasing the heating temperature of the peat-ore material promotes burnout of pores at the expense of the oxygen of the oxides.
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The introduction of iron oxides promotes the formation of a crystalline carbon structure.
References
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T. G. Plyachenov. Mercury porosimetric apparatus P-3M. L., 1961.
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W. Radmacher, P. Mohrhauer, “Brennstoff-Chemie” 36, Nos. 15, 16, 1955.
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Ya. S. Umanskii. X-ray Diffraction of Metals and Semiconductors. Moscow, Metallurgiya Publishing House, 1969.
STUDY OF THE ADSORPTION OF $\beta$-NAPHTHOL ON A MERCURY ELECTRODE FROM A SODIUM SULFATE SOLUTION
Yu. N. Oblivantsev, V. E. Gorodovykh
The effect of adsorption of surface-active substances (SAS) on the rate of an electrode process is determined by the nature and properties of the adsorption layer and of the electroactive particle. With changes in the adsorption region, the degree of coverage, the pH of the solution, etc., various effects of SAS on the kinetics and mechanism of an electrochemical reaction may be observed.
In this connection, the study of the kinetics of electrode processes in the presence of aromatic SAS is of particular interest, since for them reorientation of adsorbed molecules is possible both when the electrode potential is changed and when the concentration of SAS in the solution is changed /1/. The solution of this problem is impossible without a detailed study of the regularities of adsorp-